Deodorants are preparations, which have antimicrobial activity and which mask, remove, or decrease perspiration odor. Antiperspirants are substances, which have astringent action and inhibit the flow of perspiration. The antiperspirant/deodorant compositions may be in the form of a solid stick, an aerosol, a pump spray, a roll-on, cream, lotion, or powder. A conventional solid stick generally comprises a wax base into which the antiperspirant salts are incorporated. Roll-ons and lotions are liquid based with various possible liquids serving as the vehicle. Silicones, glycols, emollients, and etc., represent some of the suitable vehicles. A number of nonessential constituents such as suspending agents, drying agents and emollients may be added to enhance cosmetic effects.
In antiperspirant creams, the vehicle is a cream. Generally, creams contain oils and light waxes to provide the cream effect. It may also be desired to add nonessential but desirable constituents such as suspending agents, silicones, alcohol, whitening agents, and so forth. Antiperspirant powders are obviously powder based. The vehicle comprises powder constituents such as talc, kaolin, and other similar powder constituents. Other antiperspirant types include pads and gels.
Microencapsulation technology is well known in the art and is generally directed to encapsulating core materials that require protection until time of use in a protective covering. More recently, microcapsules have been developed which are “time release”. U.S. Pat. No. 5,176,903 describes the time release microcapsules, which release their core materials at a controlled rate. The result is that the core material has a longer effective life since it is not immediately released from the protective microcapsule. The benefits of controlled release are obvious. For example, when pharmaceuticals are in the controlled release format, it generally allows the user to ingest or apply one long acting dose of drug instead of being obliged to ingest many small doses throughout a time period.
The encapsulation of fragrances is well known in the art. Fragrance capsules are often found in scratch and sniff inserts in magazines, in perfumes, deodorants, and a host of other applications. An antiperspirant/deodorant containing microcapsules is disclosed in U.S. Pat. No. 5,176,903 where a fragrance oil and ester are encapsulated by a food starch and polysaccharide composition.
U.S. Pat. No. 5,876,755 discloses a composition comprising a substance encapsulated within a water-sensitive matrix (PVA and starch mixtures) so as to be releasable upon contact with water or aqueous solutions, mixed with particles of inorganic carrier material (silica) carrying a poorly water-soluble oil (perfume or fragrance), such that the composition is stable at high relative humidity. However, this mixing with silica occurs after encapsulation. Typically, a water releasable encapsulate is charged into a suitable mixer such as a ribbon mixer or a tumble mixer and fumed silica containing poorly water-soluble oil is added and mixed to obtain a homogeneous powder. If a second inorganic carrier containing poorly water-soluble oil is to be used it may be added to the mixer before addition of the fumed silica and mixing is also continued to obtain a homogeneous powder. It is desirable to develop an encapsulated dry powder for use in deodorant applications that can be produced by spray drying one emulsion without post-drying mixing or treatment.
Other systems have been described which contain starch encapsulates and also contain silicas as structuring agents in the product. These include U.S. Pat. No. 3,397,065 where an edible oil is thickened with silica. Also, encapsulated flavor has been added to chewing gum, using silica as a structuring aid (U.S. Pat. No. 3,920,849). Encapsulated fragrances have been added to fabric softeners and colognes which contained silicas as suspending agent (U.S. Pat. No. 4,446,032, U.S. Pat. No. 4,428,869). However, in these systems, the silica and starch particles are not brought into intimate contact and no interaction between the particles is disclosed. Also, no perfume or flavor ingredients were adsorbed or absorbed onto the silica particles during processing.
In the spray drying process, particles are produced by a three step operation comprising (1) forming an emulsion of the liquid core material in a solution, usually aqueous, of the normally solid coating material and (2) breaking up the emulsion into droplets of desired size, e.g., in a spray nozzle, from a spinning disc, or apertured centrifugal atomizer, and (3) removing moisture in a drying environment to solidify the coating material in the droplets to form solid particles. The drying environment may be hot drying air, e.g., in a spray drying tower, a dehydrating liquid, e.g., propylene glycol; a bed of dehydrating powder, e.g., dry starch powder; or the like. The particles produced by this process, while they may be of various sizes and shapes and may be “hollow” or “solid”, are characterized by cellular structure comprising many dispersed globules of the core material in a matrix of the coating material. “Solid” in this context means that a particle has more or less uniform structure throughout, as opposed to the “hollow” form of particle which has a shell surrounding a void, but it does not imply absence of pores or cells in the body thereof. Particles or capsules produced by this method have been used commercially in many applications, including foods where the core material is a flavoring oil and cosmetics where the core material is a fragrance oil. Cf. Balassa, Microencapsulation in the Food Industry, CRC Critical Review Journal in Food Technology, July 1971, pp 245–265; Barreto, Spray Dried Perfumes for Specialties, Soap and Chemical Specialties, December 1966; Maleeny, Spray Dried Perfumes, Soap and San Chem, January 1958, pp 135 et seq.; Flinn and Nack, Advances in Microencapsulation Techniques, Batelle Technical Review, Vo. 16, No. 2, pp 2–8 (1967); Merory, Food Flavorings, Avi Pub. Co. (1960), pp 274–277.
One of the known processes for producing microcapsules involves spraying into a drying atmosphere globules or droplets of an emulsion or solution containing, in a continuous aqueous phase, a hydrophilic colloid such as dextrin or gum Arabic as the coating material, with the addition if necessary of an emulsifier, and a volatile or non-volatile core material of organic liquid, hereafter sometimes referred to as oil or oils, in a dispersed phase. The products of this process are dry, somewhat porous powders containing roughly spherical, convoluted particles with the coating material in the solid state and with the organic liquid either dispersed as minute droplets throughout the particle, or dissolved in a solid matrix, or both, depending on the compatibility of the oil and coating material.
In the conventional spray drying process of producing capsules, the surface of the sprayed globule of the emulsion dries to form a solid outer crust almost immediately on contact with the drying atmosphere.
It was, therefore, an object of the present invention to prepare a controlled release encapsulated dry powder by a simplified spray drying process with components blended into one emulsion to arrive at a powder that requires no additional processing after spray drying and exhibits desirable solubility properties for use in a deodorant or antiperspirant.